As you might have guessed already, a room is the entity providing this functionality. You need to have at least room-aide privileges to access feature.

Citadel incorporates a RSS Feed aggregation like you may have known by the Google Reader. It polls feeds frequently and posts new entry as messages into rooms. You can use the Autopurger to expire older feed messages. This way you can use any client accessing the room (be it imap, web or even as a mailinglist) to browse feed messages.